This invention relates to the field of medical instrumentation, and more specifically to the field of microscopic analysis of fluids.
Suppliers of medical instrumentation have adopted computer technology to a high degree, offering complex and expensive equipment capable of providing rapid analyses and calculations. Such equipment has proved its worth in many situations, and indeed has paved the way to more exact, efficient diagnosis. Computerized axial tomography, for example, literally has revolutionized diagnositic techniques.
This trend, however, has bypassed some of the more mundane but essential tasks faced by the medical laboratory. Urinalysis presents an excellent example of this phenomenon. The task is relatively straightforward: a technician must view a sample through a microscope and count the number of white blood cells in a given area. Following traditional methods, the technician places a drop of sample on a microscope slide, covers that slide with a cover slide, and clips the assembly on the viewing stage of a microscope. After making the count, the two-slide assembly usually is discarded.
The answer offered by equipment suppliers is complete automation of urinalysis, combining computer-controlled chemical testing with optical scanning and pattern recognition to generate a complete report in a matter of seconds. In an era when rising medical costs are a matter of national concern, however, new equipment must not only be technically sophisticated but also cost effective. Many laboratories have rejected the automated approach after carefully weighing the savings provided versus the costs associated with the high level of capital expenditure required.
Yet, laboratories recognize that tasks such as urinalysis are expensive, labor-intensive, and repetitive. A 300-bed hospital, for example, will perform almost 23,000 urinalyses per year; at a cost of about $0.25 in disposables for each analysis, this testing results in an expenditure of almost $5700, plus the cost of technicians and microscopes, etc. This level of spending certainly does not justify the purchase of equipment priced over $100,000, but the clear requirement exists to reduce costs. What laboratories need is an approach that offers the benefits of automation without travelling as far as the fully computerized systems provided by the instrumentation industry.
The art has failed to provide effective solutions to this problem. U.S. Pat. Nos. 3,864,564, to Adkins, and 3,397,656 disclose automated systems for positioning and viewing samples, employing sophisticated logic circuitry and complex mechanisms for driving the slide in selected patterns to insure full scanning. Such approaches typify the problem rather than the solution. Similarly, Negersmith, in U.S. Pat. No. 4,300,906 presents an improvement to an automated analysis system designed to provide a constant flow of sample through the analytical portion of the system. Again, such systems do not meet the needs of the laboratories for a urinalysis system.
An optical counting system is disclosed in U.S. Pat. No. 3,511,573, issued to Isreeli, stated as being particularly useful for counting red blood cells. There, a flow cell is employed in conjunction with means for focusing a light beam, the particles being detected by utilizing photocells and photomultipliers to sense occlusions of the beam. The flow cell of this invention is itself somewhat of a complex device, requiring the machining of bores and passageways and the inclusion of a special fitting to accomodate the washing function. In like manner, a flow cell is also disclosed in U.S. Pat. No. 3,515,491, to Emary, in which the sample is retained in a machined block, within a cylindrical insert having fluid passages and a viewing bore.
What none of these devices provide is an inexpensive, easy-to-use system that will allow a laboratory to automate its urinalysis without high capital expenditure. It was left to the inventor of the present invention to solve this problem.